AT30TS750_14 Datasheet, PDF (12/51 Pages) ATMEL Corporation – Digital Temperature Sensor with Nonvolatile Registers

5.2.3
Interrupt Mode
Similar to the Comparator mode, when the device operates in the Interrupt mode, the ALERT pin will go active if the
measured temperature meets or exceeds the high temperature limit set by the T_HIGH Limit Register and a valid fault
condition exists (the consecutive number of temperature faults has been reached). Unlike the Comparator mode, the
ALERT pin will remain active until one of three normal operation events takes place: any one of the device's registers is
read, the device responds to an SMBus Alert Response Address (ARA), or the device is put into Shutdown mode.
Once the ALERT pin returns to the inactive state, it will not go active again until the measured temperature drops below
the low temperature limit set by the T_LOW Limit Register for the appropriate number of consecutive faults. Again, the
ALERT pin will remain active until one of the device's registers is read, the device responds to an SMBus ARA, or the
device is placed into the Shutdown mode.
After the ALERT pin becomes inactive again, the cycle will repeat itself with the ALERT pin going active after the
measured temperature meets or exceeds the T_HIGH Limit Register value for the proper number of consecutive faults. This
process is cyclical between T_HIGH and T_LOW temperature alarms (e.g. T_HIGH event, ALERT clear, T_LOW event, ALERT
clear, T_HIGH event, ALERT clear, T_LOW event, etc.).
In order for the ALERT pin to normally become active for the first time in the Interrupt Mode, the first event must be a
T_HIGH temperature alarm event; therefore, even if the measured temperature initially starts off between the T_HIGH and
T_LOW limits and then drops below the T_LOW temperature limit and has met valid fault conditions, the ALERT pin will still not
go active. The high temperature limit set by the T_HIGH Limit Register must be greater than the low temperature limit set by
the T_LOW Limit Register in order for the ALERT pin to activate correctly.
If switching from Comparator mode to Interrupt Mode while the ALERT pin is already active, then the ALERT pin will
remain active until it is cleared by one of the events already detailed: any one of the device's registers is read, the device
responds to an SMBus Alert Response Address (ARA), or the device is put into Shutdown Mode. The ALERT pin will
also return to the inactive state if the device receives the General Call Reset command. When reset, the contents of the
Nonvolatile Configuration Register will be copied into the Configuration Register; therefore, the device may or may not
return to the Interrupt mode depending on the setting of the NVCMP/INT bit in the Nonvolatile Configuration Register.
Figures 5-3 and Figure 5-4 show both the active high and active low ALERT pin response for a sample temperature
profile with the device configured for the Interrupt mode and a fault tolerance queue setting of two. Figure 5-4 illustrates
how the ALERT pin output would look if there was a longer delay between the ALERT trigger and the reading of a
register.
Figure 5-3. Interrupt Mode (Fault Tolerance Queue = 2)
T_HIGH Limit
Temperature
T_LOW Limit
ALERT
(Active High, POL = 1)
ALERT
(Active Low, POL = 0)
Read Register
Read Register
Read Register
Temperature Measurements/Conversions
12 AT30TS750 [Datasheet]
Atmel-8749D-DTS-AT30TS750-Datasheet_092013